Diaphragm type fluid pressure sensitive switch



Oct. 4, 1966 R. SIMONIN, JR

DIAPHRAGM TYPE FLUID PRESSURE SENSITIVE SWITCH Filed4 April 6, 1965 hf/Z W5. 25 l C Je 36 INVENTOR.

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BY HIS QTTONEYS. HnRR/s, K/c/, RUSSELL KERN 3,277,258 DIAPHRAGM TYPE FLUID f t SENSITIVE SWITCH' Rene Simonin, Jr., Downey, Calif., assig'nor to Barksdale Valves, Los Angeles,C`alif.`, a corporation of California Filed Apr. 6, 1965, Ser. No. 445,997

6Claims. (Cl.; 200g-83) This invention relates toa pressure switch and, more particularly, toga: pressure switch` having a` pressure sensingndiaphragm tightly sealed" within a housing and reL sponsive to fluid `pressureto actuate the switch.

As is wellknown, pressure switches include pressure sensing means ,anda switchV actuable in response to the sensing means.` In prior art devices, the sensing means often `includes la piston slidably mounted in a cylinder and' separated slightly therefrom byl O-rings which are providedfor, sealing purposes. One difficulty with'this arrangement is that theO-rings often stick to the walls of the cylinder particularlyl after a period of nonuse, thereby requiring an Vover-pressure to actuate the switch. T-his resnltsin an inaccuracy in the pressure level at which thenswitch operates. are also subject to leakage/of the operatingflluid around the O-rings. Use of a metal diaphrag "A, bourdon tubes is subject to similar diiculties.

An object Iofthis invention is to provide a pressure switch including relatively rateless pressure sensing means. Such Imeans eliminate the need for `a piston with O-rings, anmetal diaphragm, bellows, or a bourdon tube. The pressuresensing means is subject to almost no movement untilpthe desiredipressure is attained, Iat which time the switch is immediately actuated.

Another object ofthisinvention is to provide a pressure'switch which is easilyrmaintained `and easily cleaned ou'tifrequired. i

A fturthergobject of this invention is to provide a pressure switclji utilizing a pressure sensing means` including'ra resilientdiaphragrn which is subject tovery low distortion and, thereby achieves an increase in the'useful lifem thereof. Another object is to provide anon'- metallic diaphragm and a pressure plate in a veryshal-v lowcounterboredof a housing for limited movement therein inl response to exterior5 fluid pressure outside of `the'V housing. Switch means actuable in response `to such limitedmovement are providedpwithin the housing.l v

Still another object of this invention'is to provide a pressure switch including a pressure responsive diaphragm toimpartmovement to a pressure plate `and a piston to ac tuateaA switch and `having annularretaining meansv for retaining the diaphragm and-plate withina housing.` The annular'retaining "means serves to hold the diaphragmand4 plate securely within the housing and to provide la'tight seal against the ingress of iluid under pressure from the exteriorof the housing. It isan object. ofnthisinvention to utilize a diaphragm with an annular( beadZ and retaining meanswith an annular ring to interlock the annular zbead, the annular ring being radially inwardoffthe annular bead.' Such structure im-y` proves the seal.' between the diaphragm andthe hous' ing. Another object is,` to provide an annular spacer surroundingthe'pr'essure plate andA spacedV slightly radial: lyout'wardly therefrom to allow free axialA movement of the` preslsllire` plate. Flhe spacer helps controlmovement of 'the pressure plate and vassistsin forming av iluid'tight" seal.

A particular objectL of this invention is to provide a pressure switch asvdescrbed in the preceding paragraph and also including: an actuating 'a'r'm piyotallymounted in the housingi-otatable .in one direction in response to an'v increase in the external uid` pressure and movement Such pressure sensing' means bellows, and

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of ,the piston member inwardly to actuate the switch; spring meansV tending torotate the actuating arm in the opposite directi-om'and adjustment means for adjusting the pressure exerted by tlie 'spring' ineans 2on the actuating arni `to thereby vary the'pressure at which the switch is actuated'.`

Another object of this inventionvis to provide a pressureswitch including ai pressure responsive diaphragm for imparting movement to a pressure plate anda piston to actuate a switch, anniilar retaining meansifor re'- taining the diaphragm and plate' w'ithin'aA switch housing,"and means for'adjustinlg the amount of rrio'vement ofV the piston member.A Thestroke ofthe piston and hence' of the' pressure plate is mately .010 inch.

The invention, both as to its organization and method of operation', together with further'objects' and advantagesthereof, mayy best be understood Aby reference to thefollowing description taken in accompanying drawing:

In `the drawing:

FIG. l is an elevational view partially in section showing a diaphragm type' Huid pressure sensitive switch;

FIG. 2 isa sectionalxview4 taken along yline 2-2 in FIG. 1; i I

FIG.`3 is an enlarged fragmentary sectional view showing the pressure sensitivemeans for thel pressure switch; and

preferably adjusted to approxisilient diaphragm used in the pressure switch.

includes `a housing `12 comprising .a hollow receptacle 13 closed by"alcover 14 which is secured thereto'by a plurality ofkscrews 15.' The housing 12 has'a switch cavity 16 therein and a thick wall portion 17 which is substantially thicker than the remainder of the wall. Thethick wall portion 17 has `a cylindrical spring bore 18 andapiston bore 19therein which is parallelto and adjacent 'the spring bore.` The fbores 18` and 19 are adjacent'each other and communicate between the switch cavity 16 .andthe exterior of the thick wall `portion 17 with the spring bore being of substantially larger diameter than the pistonnbore. The housing illustrated is explosionproof; however, a standard housing may b e used ifv desired.

The outer end ofthe piston bore 19is connected to a coaxiallcylindrical counterbore 21j of a` diameter sub-k -stantiallygreater than the diameter ofithe-former and having a small axial dimension, which in the embodiment illustrated is considerably smaller than the axial-dimension of the .piston bore. The inner end of the-counterbore Z'Ivdefines anannular shoulder or 4over-pressure stop 22 theI4 plane of which issubstantially perpendicular to the longitudinall axis of4 the piston bore 19 and which isV into whichfa conduit 2,4 `which carries a plurality of con-V ductors 25 is vthreadedly secured@- A switch mounting bracket 26 which maybe'formed integrally with the-housing 12'is within the switch cavity 16.` vA -microswitch 27 which is connectedte the conductors 2,5 is mounted on the 'bracket 2 6y b`y a" screw The microswitch 27 includes a4 downwardly extending pushbutton 29, very slight inward movement of` which may either open -or close same. i The microswitch 27 may be off any suitable design. The angula1f"positior of the microswitch 27Lwithin the switch cavityfl `-may' be adjusted `by` the screw 28. A

4An actuating armz 3p 'is pivotally mounted'at its midpoint by a pin 3'0ifor pivotal movement within a channel Patented Oef.: 4 1966 connection with the FIG. 4 is an enlarged sectional view showing the re- 31 formed integrally with the housing 12. One end portion of the arm 30 is axially aligned with the piston bore 19 and another portion adjacent the other end thereof 1s axially aligned with the spring 'bore 18. The actuating arm 30 is on elongated solid, generally square 1n cross section and having an upwardly extending protrusion 32 for engaging the pushbutton 29. Rotation of the actuating arm 30 in the counterclockwise direction depresses the pushbutton 29 to actuate the microswitch 27.

Pressure responsive means are provided for imparting counterclockwise rotation to the actuating arm 30. Such means include a resilient diaphragm 33, a circular -pressure plate 34, an annular spacer 35, and a cylindrical piston member 36 journalled in the piston bore 19 for axial movement therein. As most clearly seen in FIGS. 3 and 4, the resilient diaphragm 33 spans and closes the counterbore 21 and is disposed axially outwardly of the pressure plate 34. The inner face of the diaphragm 33 engages the pressure plate 34 over a major portion of its area. The diaphragm includes an annular bead 37 adjacent its periphery and extending outwardly away from the pressure plate 34. The diaphragm 33 is constructed of a resilient nonmetallic material such as neoprene.

The spacer 35 has a circular periphery and a circular opening which surrounds the pressure plate 34 spaced slightly radially outwardly therefrom of allow free axial.

movement of the pressure plate. The spacer 35 has a at face which abuts tightly against the peripheral portions of the annular shoulder 22 and an opposed at face against which the inner side of the bead 37 is tightly pressed by means which are hereinafter described. It is preferred to utilize a thin spacer contructed of stainless steel.

The pressure -plate 34 is a thin circular, ridged stainless steel disc having a flat inner face 37a and an opposed ilat outer face 38. The outer face 38 engages the inner face of the diaphragm 33 and the inner face 37a engages the outer end of the piston 36. The pressure plate 34 is free to move slightly axially in the counterbore 21 and is engagea'ble with the annular shoulder 22 to define an innermost position thereof.

Annular retaining means 39 is provided for retaining the diaphragm 33, the spacer 35, and the pressure plate 34 within the counterbore 21. The retaining means 39 is secured to the -housing 12 by a plurality of screws 41 and contains a stepped threaded socket 42 coaxial with the piston bore 19 and into which a conduit 43 is threadedly secured. The conduit 43 supplies fluid pressure to the outer` face of the diaphragm 33. The retaining `means 39 includes an inwardly directed annular `face 44 which trrnly engages the outer face of the annular bead 37 in tight sealing relationship and causes the spacer 35 to be urged tightly against the annular Ishoulder 22. A ring 45 which is radially inwardly of the annular bead 37 interlocks with the latter in tight sealing engagement and an annular boss 46 extends inwardly into engagement with the outer face of the diaphragm 33. As the screws 41 are tightened, the annular face 44 engages the bead 37 causing the latter to flow radially into tight sealing engagement with the ring 45. Axial movement of the diaphragm 33 and the pressure plate 34 is limited by the boss 46 and the annular shoulder 22.

The outer end of the piston 36 engages the pressure plate 34 and the inner end thereof engages an end portion of the actuating arm 30. Inward movement of the diaphragm in response to a predetermined increase in tluid pressure in the conduit 43 will move the pressure plate 34 and the piston member 36 inwardly to rotate the actuating ar-m 30 counterclockwise to actuate the microswitch 27.

Means is provided for adjusting the amount of axial movement of the piston 36 in response to such increase in external fluid pressure. Such means includes an adjusting nut 47 threadedly secured on the inner end portion of the piston 36, The outer face of the nut 47 engages the wall of the switch cavity 16 adjacent the piston bore 19 and is of a type which will maintain a lixed angular orientation relative to the piston 36 after being initially set. It is apparent that by turning the nut 47, the inner end of the piston 36 and, hence, the protrusion 32 can lbe moved toward or away from the pushbutton 29. The nut 47 is preferably factory adjusted so that approximately .010 inch of movement of the pressure plate 34 and, hence, of the piston 36 and protrusion 32 is required to actuate the microswitch 27.

To resist the force of the external uid pressure acting on the outer face of the diaphragm 33, a spring 48 is provided in the spring -bore 18 which tends to rotate the actuating arm 30 in the clockwise direction. An adjustment screw 49 is screwed into the spring bore 18 adjacent and closing the outer end thereof, the screw being axially movable in the spring bore. The annular retaining means 39 has a passageway 51 extending therethrough to permit controlling of :the position of the adjusting screw 49 in the bore 18. A set screw 52 urges a soft slug 53 of metal such as copper into engagement with the side wall of the adjusting screw 49 to prevent movement thereof from the set position. The spring 48 engages the adjusting screw 49 at one end and a retainer 54 at the other end and urges the latter into engagement with the other end portion of the actuating arm 30. Thus, by adjusting the screw 49 the force of the spring and, hence, the value of Huid pressure required to actuate the microswitch 27 are adjusted.

In operation of the pressure switch, the nut 47 is adjusted to control the stroke of the piston 36. Turning of the adjusting screw 49 sets the value of uid pressure required to operate the microswitch 27. When this setting has been made, the set screw 52 is tightened to assure that such setting will be maintained. An increase in the iluid pressure in the conduit 43 will cause the diaphragm 33, the pressure plate- 34, and the piston 36 to move inwardly to rotate the actuating arm 30 counterclockwise to actuate the microswitch 27. The microswitch 27 is preferably actuated before theV plate 34 engages .the annular shoulder 22. Thus, the latter defines an over-pressure stop which limits the innermost position of the plate 34 when the diaphragm 33 is subjected to a greater pressure than is ,necessary to actuate the switch 27. Such actuation of the microswitch may result in opening or closing of one or several external circuits or the opening of one circuit and the closing of another depending upon the particular type of switch selected. Upon a decrease in fluid pressure, the force of the spring 48 will cause the actuating arm 30 to rotate clockwise to release the force on the push-button 29 and force the piston 36, plate 34, and diaphragm 33 outwardly. The passageway 22a allows axial movement of the plate 34 and diaphragm 33 within the counterbore 21 without a dashpot etfect by permitting intake and exhausting of air from the counterbore. Such release of the pushbutton 29 may have various results on the external circuitry depending upon the type of microswitch selected.

An important feature of this invention is that the diaphragm 33 and the pressure plate 34 experience only very slight axial movement prior to actuation of the microswitch 27. Thus, diaphragm distortion is reduced and the l life thereof is increased. No over-pressure is required to move the diaphragm 33 and the pressure at which the microswitch 27 is actuated may be very accurately controlled. The seal between the diaphragm 33 and the retaining means 39 `is Very tight and substantially prevents .any of the fluid under pressure in the socket 42 from passing into the switch cavity 16. The adjusting nut 47 allows accurate controlof the stroke of the piston 36, sucllll stroke preferably being in the neighborhood of .O10 mc Many changes, modifications, and substitutions can be made by one having ordinary skill in the art without departing from the spirit and scope of thisvinvention, and,

3,277,258 6A accordingly, I do not desire to be limited by the` specific a circular/pressure `plate in said counterbore adjacent embodiment described herein, but desire to be afforded to said second bore and axially movable in said the full scope ofthe following claims. counterbore;

What is claimed is:

1. In a pressure switch, the combination of a housing havingtan outside wall and aswitch cavi-ty therein, one portion of said wall being substantially thicker, than the remainder `of said wall, said portion having iirst and second cylindrical bores therein parallel to and adjacent to each other and com- Cil ajresilient diaphragm in lsaid counterbore and spanning and closing same, said diaphragm being disposed outwardly of said pressure pilate and engaging the same over amajor portion of itsarea, the outer face of said diaphragm beingy exposed to external .iluid pressure outside said wall, said diaphragm having an annular bead adjacent its periphery and-extending municatingA between saidicavity and theexterior of i outwardly away from said pressure plate; said wall, said rstbore being of substantially larger an annular spacersurrounding said pressure plate and diameter than. said second bore, the outer `end of spaced slightly radially outwardly therefrom to allow said second borel being provided-with aconnected free axial movement of said pressure plate, said cylindrical counterbore of a diameter 4substantially 15 spacer engaging said annular bead onthe inner side greatertthan the diameter of said rst bore; thereof; an actuating arm pivotally mounted in said cavi-ty ywith retaining means secured t0 said housing for clamping one end portion thereof'in alignment with saidltirst said annular bead into engagement with said spacer; bore -andanother portion thereof adjacent the other acylindrical `piston member journalled in said second endof said arm in alignment with said second bore; 2()4 *bore for axial movement therein, the outer end of electrical switch means in said cavity actuated by pivsaid piston member engaging said pressure Vplate and Qta] movement of Said actuating arm upon the octhehinner end thereof engaging said actuating arm, currence of such pivotal movement; whereby inward movement ofv said diaphragm in a circular pressure plate in said counterbore adjacent response to an increase` in said external fluid pressure to said` second` bore and axially movable in said willmove said pressure plate andtsaid piston memcounterbore; berinwardly, to rotate said actuating arm in one a resilient diaphragmtin said counterbore and spanning Adirection t0 nctuatccnid `Svvitch means;

and closing same, said.diaphragmabeing disposed outadjustment means `in said iirst bore adjacent the outer Wardly of said pressure plate and engaging the same end thereof and closing` the same, said' adjustment over a major portion of its area, the outer face of mcnS bcing nXiaiiy movable in Said iirSt bOTe and said diaphragm being exposed .to external Huid presbeingjacessiblefrom the exterior of said rSttbOrc; sure` outside said wall; and annular retaining-` means in said counterbore for retain- Springy mclnS in Said first bOfc bctWccn Said adjustment ing saidtdiaphragmand said pressure plate therein; mcanS Iand.. Said One end POftiOn` 0f Said actuating acy-lindricaltpiston member journalled in said-second arm, exerting preSSnfc ycn Said actuating armttcnding bore for axial movement therein, the outer end of to rotate Said actuating arm in a direction Opposite said piston member engaging. said. pressure plate and t0 Said One, difcctiOn, Such mOvcmcnt 0f Snidcdjustthe inner endtthereof engaging said actuating arm, mcnt mcanS varying. the pressure exerted by Said whereby inw-ard movement of said diaphragm in Spring means 0n Saidctllating armresponse to an` increase in said external fluid pres- 40 3- In nPicSSllfc SWitch,ti16.C0mbir1atiOn of: sure will move said pressure plate and said pis-ton arhOUSing having an Outside W211i and a Switch cavity member inwardly, `to rotate said lactuating arm in tnccin, Unc Portion 0f Said. Waili being Substantially `one direction to aetuate Said Switch means; thicker than the remainder of said wall, said portion adjustment means in saidrfirst bore adjacent the outer having. iifSt `and` SccOnd cylindricalV bOIleS `therein end thereof and closing the same, lsaid4 adjustment 45 Prafaiicitto and adjacent t0 cach Other andiCOmmnnimeans being axially movable lin said lirst bore and becatingri'bctwocn Said` cavity and the cXtcfiOl 0f Said ing accessiblefrom the exterior of saidirst bore; Wall, Said irStl bOre being of substantially iafgcf `and` diameter than said second bore, the 'outer end of spring means in said iirstibore between saidadjustment Said Scccndbcfc being Provided With a Iccnncctcd nnenns'and` Said one endl portion 'Ofasidacmating 50 cylindrical counterhore` of a diameter substantially arm, exerting pressure on said actuating arm tendgrfcntclthanthe diameter lOf Said fifSt bOfc, thc inner ing to rotate saidA actuating `ann in a direction oper1-.dot `said counterbor'e denins an annular shoulder; posite to said one direction; such movement of said an actuating afm pivotally mcilntcdiin Said cavity With adjustment" means varying the pressure exerted by cnc end Portion thcfccf in alignment With Said ifSt said spring means on Said actuating arnn bore and another portion thereof adjacent the other 2. In a pressure switch, the Combination of; end of said arm in alignment with said second bore; a housing having an outside walliand a switch cavity cicctficaiSWitch Incans in Said cavity actuatcdiby Pivottherein, one portion of said wall being substantially ai movement Ofi Sid actuating afmiupcn thc Occur' thicker than the remainder offsaidwall, said portion fcncc-Ofisuch Pivotal-movement? having first" and Second; cylindrical' '150mg therein 60 aA circular pressure platein said' counterbore adjacent parallel to and adjacent to each other `and communit0 Saitir Sti-cond, 'bOIc and` Xil'iy mcvabic in Said eating between said cavity and the exterior 4of said cQuntctfbQlc.; i wall, said` iirst bore being of substantially larger a. Te$ilicnt1 diaphragm inid ccuntcfborc and Spanning diameter than said secondbore, thebuter fend of and closing sme, Said ditiPhflgl'n` being, disposed said Second bore being 'provided' with a' eonnejeted 65 'outwardly ot; Saidrrenure plate and engaging the cylindricalV counterbore" of a diameter substantially Same Overlz'ar @aigri pirfioptof usare?, the Outer face greater than the diameter ofsaiizl` first bore; i of? Said diaphragm, bel-,ng eXPOSd; to exrtemai fluid an actuating, am pivotally mounted, n Santa-vio with Presufsoiltsldessl-d wat Saldtdarhragmthavmg-an one endpoirtion thereof in alignment with said. first 'annular beard' adjacent* lhspuphry and. extefndmg bore` and another portion thereof adjacent the other i Qutwardlr-y awaytromi San; pr'esiirie plate endof said arm in alignment said-.second bore' api annuiarspaer- S-umuridtntg Sal'dipressvu' plateand i i' t t i C- i i r spaced slightly radiallyoutwardly therefrom to allow electrical switch means 1n said cavity actuated by free :axial movement ofsai'd pressure plate, `said Pivotal mcvement of said actuating arm Upon thc spacer abutting Ysaid` annular shoulder andengaging occurrence of such. pivotal movement; said annular bead on the inner side thereof; i

retaining means secured to said housing for clamping said annular Ibead into engagement with said spacer and for holding said spacer firmly against said shoulder, said retaining means including an annular ring interlocking with said annular bead, said annular ring being radially inwardly of said annular bead;

a cylindrical piston member journalled in said second bore for axial movement therein, the outer end of said piston member engaging said pressure plate and the inner end thereof engaging said actuating arm, whereby inward movement of said diaphragm in response t-o an increase in said external fluid pressure will move said pressure plate and said piston member inwardly, to rotate said actuating arm in one direction to actuate said switch means;

adjustment means in said first bore adjacent the outer end thereof and closing the same, said adjustment means being axially movable in said first bore and being accessible from the exterior of said first bore; and

spring means in said first bore Ibetween said adjustment means and said one end portion of said actuating arm, exerting pressure on said actuating arm tending to rotate said actuating arm in a direction opposite to said one direction, such movement of said adjustment means varying the pressure exerted by said spring means on said actuating arm.

In a pressure switch, the combination of:

housing having an outside Wall and a switch cavity therein, one portion of said wall being substantially thicker than the remainder of said wall, said portion 'having first and second cylindrical bores therein parallel to and adjacent to each other and communicating between said cavity and the exterior of said wall, said first bore being of substantially larger diameter than said second bore, the outer end of said second bore being provided with a connected cylindrical counterbore of a diameter substantiallygreater than the diameter of said first bore and having a small axial dimension, the inner end of said counterbore defining an annular shoulder which is spaced slightly axially inwardly from the exterior of said wall;

an actuating arm pivota'lly mounted in said cavity with one end portion thereof in alignment with said first bore and another portion thereof adjacent the other end of said arm in alignment with said second bore;

electrical switch means in said cavity actuated by slight pivotal movement of said actuating arm upon the occurrence of such pivotal movement;

cir-cular pressure plate in said counterbore ladjacent to said second bore and slightly axially movable in said counterbore, sai-d pressure plate being engageable with said annular shoulder to define the innermost position of said pressure plate;

a resilient diaphragm in said counterbore'and spanning and closing same, said diaphragm being disposed outwardly of said pressure plate and engaging the same over a major portion of its area, the outer face of said diaphragm being exposed to external fiuid pressure outside said Wall, said diaphragm being movable slightly inwardly in response to said fiuid pressure until said pressure plate engages said annular shoulder;

retaining means in said counterbore for retaining said inwardly, to rotate said actuating arm in one direction to actuate said switch means;

adjustment means in said first bore adjacent the outer end thereof and closing the same, said -adjustment means being axially movable in said first bore and being accessible from the exterior of said rst bore; an-d spring means in said first bore between said adjustment means and said one end portion of said actuating arm, exerting pressure on said actuating arm tending to rotate Said actuating arm in a direction opposite to said one direction, such movement of said adjustment Imeans varying the pressure exerted by said spring means on said actuating arm.

In a pressure switch, the combination of: housing having an outside wall and a switch cavity therein, one portion of said wall being substantially thi-cker than the remainder of said wall, said portion having first and second cylindrical bores therein parallel to and adjacent to each other and communicating between said cavity and the exterior of said wall, said first bore being of substantially larger diameter than said second bore, the outer end of said second bore being provided with a connected cylinrical counterbore of a diameter substantially greater than the diameter of said first bore;

an actuating arm pivotally mounted in said cavity with one end portion thereof in alignment with said first bore and another portion thereof adjacent the other Vend of said arm in alignment with said second bore;

electrical switch means in said cavity actuated by annular retaining means in said counterbore for retaining said diaphragm and said pressure plate therein; cylindrical piston member journalled in said second bore for axial -movement therein, the outer end of said piston member engaging said pressure plate and the inner end thereof engaging said actuating arm, whereby inward 4movement `of said diaphragm in response to an increase in said external fluid pressure |will move said pressure plate and said piston member inwardly, to rotate said actuating arm in one direction to actuate said switch means;

means for adjusting the amount of axial movement of said piston member in response to said increase in said external fluid pressure;

adjustment means in said first bore adjacent the outer end thereof and closing the same, said adjustment means being axially movable in said first bore and being accessible from the exterior of said first bore; and

spring means in said first bore between said adjustment means and said one end portion of said actuating arm, exerting pressure -on said actuating arm, tending to rotate said actuating arm in a direction opposite to said one direction, such movement of said adjustment means varying the pressure exerted by said spring means on said actuating arm.

In a pressure switch, the combination of:

housing having an outside wall and a switch'cavity therein, one portion of said wall being substantially thicker than the remainder of said wall, said portion having first and second cylindrical bores therein parallel to and adjacent to each other and communicating between said cavity and the exterior of said wall, said first bore being of substantially larger diameter than said second bore, the outer end of said second bore being provided with a connected cylindrical Icounterbore of a diameter substantially greater l inwardly, to rotate said actuating arm in one direction to actuate said switch means; a threaded adjusting nut on the inner end portion of said piston for adjusting the amount of axial movethan the diameter of said first bore; ment of said piston in response to said increase in an actuating arm pivotally mounted in said cavity with said external fluid pressure, said Iadjusting nut being one end portion thereof in alignment with said first adjustable to limit said axial movement of said piston bore and another portion thereof adjacent the other to approximately .010 inch;

end of said arm in alignment with said second bore; adjustment means in said rst bore adjacent the outer electrical switch means in said `cavity actuated by end thereof and closing the same, said adjustment pivotal movement of said actuating arm upon the means being axially movable in said rst bore and occurrence of such pivotal movement; being accessible from the exterior of said rst bore; a circular pressure plate in said counterbore adjacent to and said second bore and axially movable in said counterspring means in said first bore between said adjustment bore; means and said one end portion of said actuating a resilient diaphragm in said counterbore and spanning arm, exerting pressure on said actuating arm tendand closing same, said diaphragm being disposed ing to rotate said actuating arm in a direction oppooutwardly of said pressure plate and engaging the site to said one direction, such movement of said same over a major portion of its area, the outer adjustment means varying the pressure exerted by face of said diaphragm being exposed to external said spring means on said actuating ar-m.

fluid pressure outside said wall; annular retaining means in said counterbore for re- References Cted by the Examiner taining said diaphragm and said pressure plate UNITED STATES PATENTS there@ 1,948,339 2/1934 Doeg 20o-14o X a cyllndrical piston member journalledrm said second bore for axial movement therein, the outer end of said piston member engaging said pressure plate and the inner end thereof engaging said actuating arm,

OTHER REFERENCES The English Electric Co., Ltd., February 1961, German application No. 1,099,616.

BERNARD A. GILHEANY, Primary Examiner.

GREGORY J. MAIER, Examiner.

whereby inward movement of said diaphragm in response to an increase in said external fluid pressure will ymove said pressure plate and said piston member 

1. IN A PRESSURE SWITCH, THE COMBINATION OF: A HOUSING HAVING AN OUTSIDE WALL AND A SWITCH CAVITY THEREIN, ONE PORTION OF SAID WALL BEING SUBSTANTIALLY THICKER THAN THE REMAINDER OF SAID WALL, SAID PORTION HAVING FIRST AND SECOND CYLINDRICAL BORES THEREIN PARALLEL TO AND ADJACENT TO EACH OTHER AND COMMUNICATING BETWEEN SAID CAVITY AND THE EXTERIOR OF SAID WALL, SAID FIRST BORE BEING OF SUBSTANTIALLY LARGER DIAMETER THAN SAID SECOND BORE, THE OUTER END OF SAID SECOND BORE BEING PROVIDED WITH A CONNECTED CYLINDRICAL COUNTERBORE OF A DIAMETER SUBSTANTIALLY GREATER THAN THE DIAMETER OF SAID FIRST BORE; AN ACTUATING ARM PIVOTALLY MOUNTED IN SAID CAVITY WITH ONE END PORTION THEREOF IN ALIGNMENT WITH SAID FIRST BORE AND ANOTHER PORTION THEREOF ADJACENT THE OTHER END OF SAID ARM IN ALIGNMENT WITH SAID SECOND BORE; ELECTRICAL SWITCH MEANS IN SAID CAVITY ACTUATED BY PIVOTAL MOVEMENT OF SAID ACTUATING ARM UPON THE OCCURRENCE OF SUCH PIVOTAL MOVEMENT; A CIRCULAR PRESSURE PLATE IN SAID COUNTERBORE ADJACENT TO SAID SECOND BORE AND AXIALLY MOVABLE IN SAID COUNTERBORE; A RESILIENT DIAPHRAGM IN SAID COUNTERBORE AND SPANNING AND CLOSING SAME, SAID DIAPHRAGM BEING DISPOSED OUTWARDLY OF SAID PRESSURE PLATE AND ENGAGING THE SAME OVER A MAJOR PORTION OF ITS AREA, THE OUTER FACE OF SAID DIAPHRAGM BEING EXPOSED TO EXTERNAL FLUID PRESSURE OUTSIDE SAID WALL; ANNULAR RETAINING MEANS IN SAID COUNTERBORE FOR RETAINING SAID DIAPHRAGM AND SAID PRESSURE PLATE THEREIN; A CYLINDRICAL PISTON MEMBER JOURNALLED IN SAID SECOND BORE FOR AXIAL MOVEMENT THEREIN, THE OUTER END OF SAID PISTON MEMBER ENGAGING SAID PRESSURE PLATE AND THE INNER END THEREOF ENGAGING SAID ACTUATING ARM, WHEREBY INWARD MOVEMENT OF SAID DIAPHRAGM IN RESPONSE TO AN INCREASE IN SAID EXTERNAL FLUID PRESSURE WILL MOVE SAID PRESSURE PLATE AND SAID PISTON MEMBER INWARDLY, TO ROTATE SAID ACTUATING ARM IN ONE DIRECTION TO ACTUATE SAID SWITCH MEANS; ADJUSTMENT MEANS IN SAID FIRST BORE ADJACENT THE OUTER END THEREOF AND CLOSING THE SAME, SAID ADJUSTMENT MEANS BEING AXIALLY MOVABLE IN SAID FIRST BORE AND BEING ACCESSIBLE FROM THE EXTERIOR OF SAID FIRST BORE; AND SPRING MEANS IN SAID FIRST BORE BETWEEN SAID ADJUSTMENT MEANS AND SAID ONE END PORTION OF SAID ACTUATING ARM, EXERTING PRESSURE ON SAID ACTUATING ARM TENDING TO ROTATE SAID ACTUATING ARM IN A DIRECTION OPPOSITE TO SAID ONE DIRECTION, SUCH MOVEMENT OF SAID ADJUSTMENT MEANS VARYING THE PRESSURE EXERTED BY SAID SPRING MEANS ON SAID ACTUATING ARM. 